Positive commandment · Mitzvat Aseh #145 of 613
Law of one who dedicates from his properties, that it is of the priests
לדון בדיני חרמים, מהם לה' ומהם לכוהן
The verse · Vayikra 27:28
אַךְ־כׇּל־חֵרֶם אֲשֶׁר יַחֲרִם אִישׁ לַה׳ מִכׇּל־אֲשֶׁר־לוֹ מֵאָדָם וּבְהֵמָה וּמִשְּׂדֵה אֲחֻזָּתוֹ לֹא יִמָּכֵר וְלֹא יִגָּאֵל כׇּל־חֵרֶם קֹדֶשׁ־קׇדָשִׁים הוּא לַה׳
“Notwithstanding no devoted thing, that a man shall devote to the Lord of all that he has, both of man and beast, and of the field of his possession, shall be sold or redeemed: every devoted thing is most holy to the Lord.”
The Rambam’s words
To render judgment with regard to property which is dedicated, whether dedicated to G-d or dedicated to the priests, as [Leviticus 27:28] states: "However, any dedication that will be made...."
לדון בדיני חרמים, מהם לה' ומהם לכוהן, שנאמר: "אך כל חרם אשר יחרים" (ויקרא כז,כח).
Why · Sefer HaChinuch #357
Law of one who dedicates from his properties, that it is of the priests
“It is from the roots of the commandment [that it is] because Israel is the nation that G-d chose from all the other nations for His service and to recognize His Name, and they are not under the rule of the constellations that G-d apportioned to all the other nations.”
Who & when
“And [it] is practiced at the time of the [Temple] by males and females.”
Where in the Mishneh Torah
Hilchot Appraisals and Devoted Property הלכות ערכים וחרמין